U.S. patent application number 10/969914 was filed with the patent office on 2005-06-02 for donor substrate for laser induced thermal imaging method and organic electroluminescence display device fabricated using the substrate.
Invention is credited to Kang, Tae-Min, Kim, Mu-Hyun, Lee, Seong-Taek.
Application Number | 20050118525 10/969914 |
Document ID | / |
Family ID | 34617388 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050118525 |
Kind Code |
A1 |
Kim, Mu-Hyun ; et
al. |
June 2, 2005 |
Donor substrate for laser induced thermal imaging method and
organic electroluminescence display device fabricated using the
substrate
Abstract
A donor substrate for laser induced thermal imaging method and
an electroluminescence display device fabricated using the donor
substrate and provides an organic electroluminescence display
device having superior characteristics of emitting layer by
protecting transfer layer from excessive heat by providing a donor
substrate for laser induced thermal imaging comprising a base
substrate, a light-heat converting layer formed on an upper part of
the base substrate; and a transfer layer formed on an upper part of
the light-heat converting layer and formed of an organic material,
wherein a light absorbing material contained in the light-heat
converting layer to generate heat by absorbing laser has a
concentration gradient in a direction form a base substrate side to
a transfer layer side in the light-heat converting layer, and an
organic electroluminescence display device fabricated using the
donor substrate.
Inventors: |
Kim, Mu-Hyun; (Suwon-si,
KR) ; Kang, Tae-Min; (Suwon-si, KR) ; Lee,
Seong-Taek; (Suwon-si, KR) |
Correspondence
Address: |
Robert E. Bushnell
Suite 300
1522 K Street, N.W.
Washington
DC
20005
US
|
Family ID: |
34617388 |
Appl. No.: |
10/969914 |
Filed: |
October 22, 2004 |
Current U.S.
Class: |
430/200 ;
430/270.1; 430/964 |
Current CPC
Class: |
H01L 51/56 20130101;
B41M 5/46 20130101; H01L 51/0013 20130101; B41M 5/38214
20130101 |
Class at
Publication: |
430/200 ;
430/270.1; 430/964 |
International
Class: |
G03C 001/76 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2003 |
KR |
2003-86123 |
Claims
What is claimed is:
1. A donor substrate for laser induced thermal imaging comprising:
a base substrate; a light-heat converting layer formed on the base
substrate; and a transfer layer formed on the light-heat converting
layer and formed of an organic material, wherein a light absorbing
material contained in the light-heat converting layer to generate
heat by absorbing laser has a concentration gradient in a direction
form a base substrate side to a transfer layer side in the
light-heat converting layer, and the light-heat converting layer
has a thickness of 2 to 10 .mu.m.
2. The donor substrate for laser induced thermal imaging according
to claim 1, wherein the light-heat converting layer is formed by
mixing the light absorbing material with a polymer bonding
resin.
3. The donor substrate for laser induced thermal imaging according
to claim 1, wherein the light absorbing material is a material
selected from the group consisting of carbon black, graphite,
infrared dyes, infrared pigments and dyes.
4. The donor substrate for laser induced thermal imaging according
to claim 2, wherein the polymer bonding resin is a material
selected from the group consisting of a (meta)acrylate oligomer
selected from the group consisting of acryl (meta)acrylate
oligomer, ester (meta)acrylate oligomer, epoxy (meta)acrylate
oligomer and urethane (meta)acrylate oligomer, a mixture of the
(meta)acrylate oligomer and (meta)acrylate monomer, and
(meta)acrylate monomer.
5. The donor substrate for laser induced thermal imaging according
to claim 1, wherein the light-heat converting layer has a thickness
of 3 to 7 .mu.m.
6. The donor substrate for laser induced thermal imaging according
to claim 1, wherein the concentration gradient is continuous.
7. The donor substrate for laser induced thermal imaging according
to claim 1, wherein the concentration gradient is
discontinuous.
8. The donor substrate for laser induced thermal imaging according
to claim 1, wherein optical density of the light-heat converting
layer is 2.0 or less.
9. The donor substrate for laser induced thermal imaging according
to claim 8, wherein optical density of the light-heat converting
layer is 1.5 or less.
10. A donor substrate for laser induced thermal imaging comprising:
a base substrate; a light-heat converting layer having a thickness
of 2 to 10 .mu.m formed on the base substrate; and a transfer layer
formed on the light-heat converting layer.
11. The donor substrate for laser induced thermal imaging according
to claim 10, wherein a light absorbing material for generating heat
by absorbing laser is contained in the light-heat converting layer
in a uniformed concentration.
12. The donor substrate for laser induced thermal imaging according
to claim 10, wherein the light-heat converting layer is formed by
mixing the light absorbing material with a polymer bonding
resin.
13. The donor substrate for laser induced thermal imaging according
to claim 10, wherein the light absorbing material is a material
selected from the group consisting of carbon black, graphite,
infrared dyes, infrared pigments and dyes.
14. The donor substrate for laser induced thermal imaging according
to claim 12, wherein the polymer bonding resin is a material
selected from the group consisting of a (meta)acrylate oligomer
selected from the group consisting of acryl (meta)acrylate
oligomer, ester (meta)acrylate oligomer, epoxy (meta)acrylate
oligomer and urethane (meta)acrylate oligomer, a mixture of the
(meta)acrylate oligomer and (meta)acrylate monomer, and
(meta)acrylate monomer.
15. The donor substrate for laser induced thermal imaging according
to claim 10, wherein optical density of the light-heat converting
layer is 2.0 or less.
16. The donor substrate for laser induced thermal imaging according
to claim 10, wherein optical density of the light-heat converting
layer is 1.5 or less.
17. The donor substrate for laser induced thermal imaging according
to claim 11, wherein the heat generated by the light absorbing
material causes the transfer layer to transfer when forming an
organic electroluminescence display device.
18. An organic electroluminescence display device fabricated using
the donor substrate for laser induced thermal imaging of claim 1.
Description
CLAIM OF PRIORITY
[0001] This application makes reference to, incorporates the same
herein, and claims all benefits accruing under 35 U.S.C. .sctn.119
from an application for DONOR FILM FOR LASER INDUCED THERMAL
IMAGING METHOD AND ELECTROLUMINESCENCE DISPLAY DEVICE MANUFACTURED
USING THE SAME FILM earlier filed in the Korean Intellectual
Property Office on 29 Nov. 2003 and there duly assigned Serial No.
2003-86123.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the invention
[0003] The present invention relates to a donor substrate for laser
induced thermal imaging method and an organic electroluminescence
display device fabricated using the substrate, more particularly,
to a donor substrate used for forming an organic layer for organic
electroluminescence display device and an organic
electroluminescence display device using the substrate.
[0004] 2. Description of Related Art
[0005] Generally, an organic electroluminescence display device is
formed of various layers including anode and cathode, hole
injecting layer, hole transporting layer, light-emitting layer,
electron transporting layer and electron injecting layer. The
organic electroluminescence display device is divided into high
molecular organic electroluminescence display device and small
molecular organic electroluminescence display device according to
materials used in the organic electroluminescence display device,
wherein respective layers are introduced into the organic
electroluminescence display device by vacuum deposition in case of
the small molecular organic electroluminescence display device
while an emitting device is fabricated in the organic
electroluminescence display device by using spin-coating process in
case of the high molecular organic electroluminescence display
device.
[0006] When fabricating a single color device, a high molecular
organic electroluminescence display device is simply fabricated
using a spin coating process, wherein the high molecular organic
electroluminescence display device has demerits that emission
efficiency and life cycle are dropped although driving voltage is
lower compared to a small molecular organic electroluminescence
display device. Furthermore, when fabricating a full color device
in which red, green and blue high molecules are patterned, the high
molecular organic electroluminescence display device has problems
that emission characteristics including emission efficiency and
life cycle are deteriorated when using inkjet technology or a laser
induced thermal imaging method.
[0007] Particularly, when patterning a single high molecular
organic electroluminescence display device using a laser induced
thermal imaging method, most of materials are not transferred on
the single high molecular organic electroluminescence display
device.
[0008] A method for forming patterns of a high molecular organic
electroluminescence display device by laser induced thermal imaging
method is disclosed in U.S. Pat. No. 5,998,085 to Thomas A. Isberg
et al. and titled PROCESS FOR PREPARING HIGH RESOLUTION EMISSIVE
ARRAYS AND CORRESPONDING ARTICLES, U.S. Pat. No. 6,214,520 to
Martin B. Wolk et al. and titled THERMAL TRANSFER ELEMENT FOR
FORMING MULTILAYER DEVICES and U.S. Pat. No. 6,114,088 to Martin B.
Wolk et al. and titled THERMAL TRANSFER ELEMENT FOR FORMING
MULTILAYER DEVICES.
[0009] In order to apply the laser induced thermal imaging method,
at least light source, transfer substrate and substrate are
required, and light coming out of the light source is absorbed into
a light absorption layer of the transfer substrate and converted
into a thermal energy so that a transfer layer forming material of
the transfer substrate is transferred onto the substrate by the
thermal energy, thereby forming a desired image as disclosed in
U.S. Pat. No. 5,220,348 to David P. D'Aurelio and titled ELECTRONIC
DRIVE CIRCUIT FOR MULTI-LASER THERMAL PRINTER, U.S. Pat. No.
5,256,506 to Ernest W. Ellis et al. and titled ABLATION-TRANSFER
IMAGING/RECORDING, U.S. Pat. No. 5,278,023 to Richard E. Bills et
al. and titled PROPELLANT-CONTAINING THERMAL TRANSFER DONOR
ELEMENTS and U.S. Pat. No. 5,308,737 to Richard E. Bills et al. and
titled LASER PROPULSION TRANSFER USING BLACK METAL COATED
SUBSTRATES.
[0010] The laser induced thermal imaging method is used in
fabrication of a color filter for liquid crystal display device and
used to form patterns of emitting materials as disclosed in U.S.
Pat. No. 5,998,085.
[0011] U.S. Pat. No. 5,937,272 to Ching W. Tang and titled
PATTERNED ORGANIC LAYERS IN A FULL-COLOR ORGANIC ELECTROLUMINESCENT
DISPLAY ARRAY ON A THIN FILM TRANSISTOR ARRAY SUBSTRATE relates to
a method for forming a high quality patterned organic layer in a
full color organic electroluminescence display device, and a donor
supporting body obtained by coating an organic electroluminescence
substance with a transferable coating material is used in the
method. The donor supporting body is heated so that the organic
electroluminescence substance is transferred onto a recess surface
part of substrate for forming a colorized organic
electroluminescence medium positioned in a targeted lower pixel,
wherein the organic electroluminescence substance is vaporized to
be transferred onto the pixel by applying heat or light to a donor
substrate.
[0012] It is disclosed in U.S. Pat. No. 5,688,551 to Jon Eric
Littman et al. and titled METHOD OF FORMING AN ORGANIC
ELECTROLUMINESCENT DISPLAY PANEL that sub-pixels are formed on each
pixel region by transferring organic electroluminescence substance
from donor sheet to receiver sheet, wherein the sub-pixels are
formed by transferring an organic electroluminescence substance
having sublimation property from the donor sheet to the receiver
sheet at low temperature of about 400.degree. C. or less in the
transferring process.
[0013] U.S. Pat. No. 6,228,555 to Thomas R. Hoffend, Jr. et al.
entitled THERMAL MASS TRANSFER DONOR ELEMENT discusses a thermal
mass transfer donor element is provided that includes a thermal
transfer layer and a light-to-heat conversion layer, wherein the
light-to-heat conversion layer has at least two regions exhibiting
different absorption coefficients.
SUMMARY OF THE INVENTION
[0014] Therefore, in order to solve problems in the prior art, it
is an object of the present invention to provide a donor substrate
for laser induced thermal imaging which is capable of preventing
degeneration of transfer layer due to excessive temperature when
forming an organic film layer comprising an emitting layer by laser
induced thermal imaging during fabrication of an organic
electroluminescence display device.
[0015] In order to achieve the foregoing object, the present
invention provides a donor substrate for laser induced thermal
imaging comprising a base substrate, a light-heat converting layer
formed on an upper part of the base substrate, and a transfer layer
formed on an upper part of the light-heat converting layer and
formed of an organic material, wherein a light absorbing material
contained in the light-heat converting layer to generate heat by
absorbing laser has a concentration gradient in a direction form a
base substrate side to a transfer layer side in the light-heat
converting layer.
[0016] Furthermore, the present invention provides an organic
electroluminescence display device characterized in that it is
fabricated using the donor substrate for laser induced thermal
imaging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] A more complete appreciation of the present invention, and
many of the attendant advantages thereof, will become readily
apparent as the same becomes better understood by reference to the
following detailed description when considered in conjunction with
the accompanying drawings in which like reference symbols indicate
the same or similar components, wherein:
[0018] FIG. 1 is a cross sectional view for showing structure of
one example of a full color organic electroluminescence display
device;
[0019] FIG. 2 is a cross sectional view for showing structure of
one example of a donor substrate for laser induced thermal imaging
method;
[0020] FIG. 3 is a drawing for showing a transfer model in case of
using the donor substrate of FIG. 2;
[0021] FIG. 4 is a drawing for illustrating transfer mechanism when
transfer patterning an organic emitting film used in an organic
electroluminescence display device by using laser according to the
present invention;
[0022] FIG. 5 is a drawing for showing structure of a donor
substrate for laser induced thermal imaging method according to a
preferred embodiment of the present invention;
[0023] FIG. 6 is a graph for showing efficiency of an organic
electroluminescence display device according to thickness and
absorption ratio of light-heat converting layer according to the
present invention; and
[0024] FIG. 7 is a drawing for describing a method for laser
induced thermal imaging using a donor substrate according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] FIG. 1 is a cross sectional view for showing structure of
one example of a full color organic electroluminescence display
device.
[0026] Referring to FIG. 1, first electrode 200 is patterned thus
formed on an insulating substrate 100. The first electrode 200 is
formed of a transparent electrode in case of a bottom emitting type
full color organic electroluminescence display device and formed of
a conductive metal comprising a reflection film in case of a top
emitting type full color organic electroluminescence display
device.
[0027] A pixel defining layer (PDL) 300 is formed of an insulating
material on an upper part of the first electrode 200 to define
pixel region and insulate between emitting layers.
[0028] An organic film layer 330 comprising an organic
light-emitting layer is formed on the pixel region defined by the
pixel defining layer (PDL) 300, and the organic film layer 330
further comprises one or more of layers selected from hole
injecting layer, hole transporting layer, hole blocking layer,
electron transporting layer and electron injecting layer besides
the organic light-emitting layer, wherein both high molecular
substance and small molecular substance can be used as the organic
light-emitting layer.
[0029] Second electrode 400 is formed on the organic film layer
330, after forming the organic film layer 330, and the pixel
defining layer (PDL) 300. The second electrode 400 is formed of a
conductive metal layer comprising the reflection film if the first
electrode 200 is a transparent electrode, and formed of a
transparent electrode if the first electrode 200 is a conductive
metal layer comprising the reflection film. An organic
electroluminescence display device is completed by sealing the
organic electroluminescence display device after forming the second
electrode 400.
[0030] However, as illustrated in FIG. 2, a donor substrate 34 for
laser induced thermal imaging comprises base substrate 31,
light-heat converting layer 32 and transferring layer 33 and
further comprises a buffer layer (not shown on FIG. 2) in case of
forming a light-emitting layer using laser induced thermal
imaging.
[0031] FIG. 3 relates to a transfer model in case of using a donor
substrate. The transfer layer is separated from a base substrate
and transferred to a substrate of an organic electroluminescence
display device as a transfer layer 33 is being expanded according
to expansion of a light-heat converting layer 32 during laser
irradiation as illustrated in FIG. 3. Therefore, there are problems
in that excessive temperature results in defects or degeneration of
emitting materials during patterning if heat changed is not
controlled often since a patterned material is transferred onto a
lower substrate through an energy for converting laser beam into
heat.
[0032] The present invention will now be described in detail in
connection with preferred embodiments with reference to the
accompanying drawings. For reference, like reference characters
designate corresponding parts throughout several views.
[0033] FIG. 4 is a drawing for illustrating transfer mechanism when
transfer patterning an organic emitting film used in an organic
electroluminescence display device by using laser according to the
present invention.
[0034] A mechanism for transfer patterning an organic film S2 using
an ordinary laser is that the organic film S2 should be separated
from a part on which a laser beam is not irradiated as an organic
film S2 adhered to a substrate S1 is being detached from the
substrate S1 to be transferred to a substrate S3 by action of laser
as illustrated in FIG. 4.
[0035] Factors for affecting transfer characteristics are first
adhesive force W12 between substrate S1 and substrate S2, adhesion
force W22 of the substrate S2, and second adhesive force W23
between the substrate S2 and substrate S3.
[0036] The first and second adhesive forces and adhesion force are
represented as in the following expressions using surface tensions
.gamma.1, .gamma.2 and .gamma.3 and interfacial tensions .gamma.12
and .gamma.23 of respective layers.
W12=.gamma.1+.gamma.2-.gamma.3
W22=2.gamma.2
W23=.gamma.2+.gamma.3-.gamma.23
[0037] In order to improve laser transfer characteristics, the
adhesion force of a substrate should be less than adhesive forces
between the respective substrates.
[0038] Generally, an organic material is used in an organic
electroluminescence display device as a material for forming
respective layer of the organic electroluminescence display device,
and fine patterns of light-emitting layer can be formed by
transferring an emitting material 433 from a donor substrate 434 to
the organic electroluminescence display device 400, thereby
generating mass transition 450 since the first and second adhesive
forces are greater than the adhesion force if a small molecular
material is used as the organic material. The fine patterns of the
light-emitting layer can formed, and possibility of mis-alignment
is decreased by transferring the light-emitting material 433 from
the donor substrate 434 to the organic electroluminescence display
device.
[0039] FIG. 5 is a drawing for showing structure of a donor
substrate 434 for laser induced thermal imaging method according to
first preferred embodiment of the present invention.
[0040] Referring to FIGS. 4 and 5, the donor substrate 434 has a
structure comprising a base substrate 431, a light-heat converting
layer 432 formed on base substrate 431, and a transfer layer 433
formed on the light-heat converting layer 432 and laid up all over
the base substrate 431.
[0041] The donor substrate 434 of can be used with structure of the
substrate being changed according to its applications. For example,
a buffer layer (not illustrated on FIG. 5) for protecting a gas
generating layer (not illustrated on FIG. 5) or the light-heat
converting layer 432 can be additionally formed between light-heat
converting layer 432 and base substrate 431 to improve sensitivity
of the substrate.
[0042] The base substrate 431 is formed of transparent polymers
including polyester such as polyethylene terephthalate, polyacryl
resin, polyepoxy, polyethylene, and polystyrene. Particularly, a
polyethylene terephthalate film is mainly used as the transparent
polymer. It is preferable that the base substrate 431 has a
thickness of 10 to 500 .mu.m. The base substrate functions as a
supporting substrate, and a composite multi-component substrate can
be also used as the base substrate.
[0043] The light-heat converting layer 432 comprises a light
absorbing material having a property for absorbing light in the
infrared ray-visible ray range. The light absorbing material
includes colorants such as carbon black, graphite, infrared dyes,
infrared pigments and dyes, and a polymer bonding resin for fixing
the light absorbing material. That is, the light-heat converting
layer 432 is formed by mixing the light absorbing material with the
polymer bonding resin.
[0044] It is preferable that the carbon black or graphite has a
grain size of 0.5 .mu.m or less, and ordinary pigments or dyes are
used as the pigments or dyes.
[0045] On the other hand, the polymer bonding resin is is a
material selected from the group consisting of a (meta)acrylate
oligomer selected from the group consisting of acryl (meta)acrylate
oligomer, ester (meta)acrylate oligomer, epoxy (meta)acrylate
oligomer and urethane (meta)acrylate oligomer, a mixture of the
(meta)acrylate oligomer and (meta)acrylate monomer, and
(meta)acrylate monomer.
[0046] The optical density of the light-heat converting layer 432
is 2.0 or less, and is preferably 1.5 or less, wherein the optical
density is amount of light when luminosity becomes the certain
intensity after light having certain intensity and wavelength
passes through a solution layer. An amount of light transmitted to
a transfer layer after passing through the light-heat converting
layer is increased.
[0047] Therefore, as energy transferred to a transfer layer 433
through the light-heat converting layer 432 is high, it is not
preferable that the optical density of the light-heat converting
layer 432 is 2.0 or more since the transfer layer can be damaged by
thermal energy.
[0048] Furthermore, amount of heat transferred to the transfer
layer 433 is controlled so that the transfer layer 433 is not
damaged by heat by forming the light-heat converting layer 432 in
such a way that a light absorbing material is not uniformly mixed
with polymer bonding resin, and the closer the light-heat
converting layer 432 is to the transfer layer 433, the lower the
concentration of the light absorbing material is, thereby lowering
light absorbing ratio of laser beam as the light-heat converting
layer 432 is getting closer to the transfer layer 433 so that a
conversion amount of light into heat is lowered.
[0049] Therefore, a donor substrate 434 of the present invention is
formed in such a manner that the light absorbing material contained
in the polymer bonding resin has a concentration gradient so that
concentration of the light absorbing material contained in the
polymer bonding resin is high at the side closer to the base
substrate 431, and the closer the donor substrate 434 is to the
transfer layer 433, the lower concentration of the light absorbing
material is.
[0050] The donor substrate 434 is formed in such a way that the
concentration gradient is continuously varied, and the light-heat
converting layer 432 is discontinuously formed.
[0051] On the other hand, heat transferred to the transfer layer
433 is controlled by forming the light-heat converting layer 432 in
such a manner that concentration of the light absorbing material
contained in the polymer bonding resin is changed, and thickness d
of the light-heat converting layer 432 is formed to a certain
thickness or more as constantly maintaining concentration of the
light absorbing material.
[0052] If the thickness d of the light-heat converting layer 432 is
too thin, the energy absorption ratio is lowered so that expansion
pressure is lowered due to low light-heat converting energy, and
transmission energy is increased so that substrate circuits of an
organic electroluminescence display device are damaged
accordingly.
[0053] Furthermore, an edge open defect of the transfer layer,
caused by a stepped surface level generated by a pixel defining
film for defining pixel region of an organic electroluminescence
display device, is reduced only by maintaining the light-heat
converting layer 432 to a certain thickness or less when the
light-heat converting layer 432 is expanded by laser energy during
laser induced thermal imaging, thereby decreasing a radius of
curvature during expansion of the light-heat converting layer
432.
[0054] It is not preferable that the light-heat converting layer
432 be too thick since laser energy is not transferred to the
light-heat converting layer as a whole during laser irradiation,
resulting in defective transfer characteristics.
[0055] Therefore, the light-heat converting layer 432 has a
thickness of 2 to 10 .mu.m, preferably 3 to 7 .mu.m.
[0056] Furthermore, heat transferred to the transfer layer 433 is
controlled by forming the polymer bonding resin composing the
light-heat converting layer 432 to a certain thickness or more
while maintaining a certain concentration gradient of the
light-heat converting layer 432, wherein the concentration gradient
is continuous or discontinuous so that concentration of the
light-heat converting layer 432 is formed, and thickness of the
light-heat converting layer is 2 to 10 .mu.m, preferably 3 to 7
.mu.m.
[0057] An organic film containing the light absorbing material is
formed by ordinary film coating methods including extrusion, spin
and knife coating.
[0058] FIG. 6 is a graph for showing emission efficiency of an
organic electroluminescence display device according to a thickness
and absorption ratio, in which it can be seen that the thicker the
thickness of the light-heat converting layer is, the higher the
emission efficiency of the organic electroluminescence display
device is if absorption ratio of the light absorbing material is
constant, when comparing areas (4), (5) and (6) with each
other.
[0059] Furthermore, it can be seen in FIG. 6 that the higher the
absorption ratio of the light absorbing material is, the lower the
emission efficiency of the organic electroluminescence display
device is if the light-heat converting layer 432 is constant when
comparing (2) with (5).
[0060] Therefore, it can be seen from (6) and (8) in FIG. 6 that
the organic electroluminescence display device has the highest
emission efficiency when the light-heat converting layer has
constant thickness and low light absorbing ratio.
[0061] On the other hand, the gas generating layer plays a role of
providing transfer energy by causing decomposition reaction as
absorbing light or heat, thereby emitting nitrogen gas or hydrogen
gas, and the gas generating layer is formed of a material selected
from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT),
etc.
[0062] On the other hand, the transfer layer 433 is formed of at
least one material selected from high or small molecular organic
electroluminescence material, hole transfer organic material and
electron transfer organic material so that the transfer layer 433
corresponds to characteristics of an organic electroluminescence
display device to be fabricated, wherein the transfer layer 433 is
formed to a coating thickness of 100 to 50,000 .ANG. by ordinary
coating methods including extrusion, spin-coating, knife coating,
vacuum deposition and chemical vapor deposition (CVD).
[0063] As described in the above, characteristics of the transfer
layer are prevented from being deteriorated by forming the
light-heat converting layer 432 to a thick thickness and having
light absorbing layer maintain a certain concentration gradient
according to the thickness of the light absorbing layer or forming
the light-heat converting layer 432 to a certain thickness or more,
thereby lowering temperature of the light-heat converting layer 432
transferred to the transfer layer.
[0064] Fine patterns are easily formed on a donor substrate for
laser induced thermal imaging disclosed in the present invention,
particularly when an emission device is an organic
electroluminescence display device formed of an organic
material.
[0065] Referring to FIG. 7, a method for forming fine patterns of
organic thin film on an organic electroluminescence display device
using a donor substrate according to the present invention is
described in detail as follows. Application of the donor substrate
of the present invention is not limited to the organic
electroluminescence display device although an organic
electroluminescence display device is mentioned as one application
example of a donor substrate of the present invention for
convenience of description in the following description.
[0066] FIG. 7 is a drawing for explaining a method for performing
laser induced thermal imaging using a donor substrate 434 according
to the present invention. First, a transparent electrode layer 400
is formed on a transparent substrate 500. Separately from the
transparent electrode layer, a donor substrate 434 is prepared by
sequentially coating the light-heat converting layer 432 and the
transfer layer 433 on the base substrate 431.
[0067] The transfer layer 433 is formed by coating an organic thin
film forming material on the light-heat converting layer 432,
wherein a certain content of additive can be added to the transfer
layer to improve various characteristics of the transfer layer. For
example, dopant can be added to the transfer layer to increase
efficiency of light-emitting layer. The transfer layer 433 is
formed by using ordinary film coating methods such as extrusion,
spin coating and knife coating.
[0068] The transfer layer 433 is formed by laying up one or two
layers of the foregoing organic film.
[0069] After forming the transfer layer 433, the donor substrate
434 is arranged at a position spaced apart from the transparent
electrode layer 400 formed substrate 500 in a certain distance, and
an energy source 437 is irradiated onto the donor substrate
434.
[0070] The energy source 437 activates the light-heat converting
layer 432 by passing through base substrate 431 via a transfer
apparatus and emits heat by pyrolysis reaction caused by the light
absorbing material contained in the light-heat converting layer
432.
[0071] As the light-heat converting layer 432 of the donor
substrate 434 is being expanded by the emitted heat, the transfer
layer 433 is separated from the donor substrate 434 so that a
light-emitting layer that is a transfer material is transferred as
a desired pattern and thickness on a pixel region defined by pixel
defining layer on an upper part of an organic electroluminescence
display device.
[0072] However, it is necessary to control heat transferred since
the produced heat is transferred to the transfer layer 433 to
damage the transfer layer 433 if much of heat is emitted by the
pyrolysis reaction as described in the above.
[0073] Therefore, the heat transferred to the transfer layer 433 is
controlled to protect the transfer layer 433 by forming the
light-heat converting layer 432 in such a manner that concentration
of the light absorbing material contained in the polymer bonding
resin for forming the light-heat converting layer 432 is lowered
from the substrate (431) side to the transfer layer (433) side so
that the closer the light-heat converting layer 432 is, the less
amount of heat produced by pyrolysis reaction caused by light
is.
[0074] The concentration gradient of the light absorbing material
can be continuously formed or discontinuously formed.
[0075] Additionally, less amount of heat is transferred to the
transfer layer 433 as a light and heat transfer passageway is being
lengthened by constantly maintaining concentration of the light
absorbing material and maintaining thickness of a polymer bonding
resin composing the light-heat converting layer 432 to a certain
thickness, wherein thickness of the light-heat converting layer 432
is 2 to 10 .mu.m, preferably 3 to 7 .mu.m.
[0076] Furthermore, heat transferred to the transfer layer 433 is
controlled by forming the polymer bonding resin composing the
light-heat converting layer 432 to a certain thickness or more as
maintaining a certain concentration gradient of the light-heat
converting layer 432, wherein the concentration gradient is
continuous or discontinuous so that a concentration layer is
formed, and thickness of the light-heat converting layer 432 is 2
to 10 .mu.m, preferably 3 to 7 .mu.m.
[0077] On the other hand, a laser, xenon (Xe) lamp, flash lamp,
etc. can be used as an energy source in the present invention. The
laser among the energy sources is preferably used since it obtains
the most superior transfer effect, wherein all general lasers
including solid, gas, semiconductor and dyes are used as the laser,
and a circular or other shaped laser beam can be used.
[0078] A heat treatment process for solidifying and adhering
transferred material is performed after performing the foregoing
transfer process.
[0079] The laser induced thermal imaging of the transfer material
is performed in one step or multi-steps. That is, an organic thin
film layer to be transferred is formed to a required thickness by
one transfer or several repeated transfers. However, it is
preferable that the organic thin film layer is formed by one
transfer considering process convenience and stability.
[0080] As described in the above, the present invention prevents
characteristics of a light-emitting layer formed on the transfer
layer from being deteriorated by the heat by forming the light-heat
converting layer in such a way that the light absorbing material
contained in the light-heat converting layer of a donor substrate
for laser induced thermal imaging has a concentration gradient, or
the light-heat converting layer is formed to a certain thickness or
more, thereby decreasing amount of heat transferred to the transfer
layer.
[0081] While the invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that the foregoing and
other changes in form and details may be made therein without
departing from the spirit and scope of the invention.
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